Alloy for dental plates



Patented Nov. 9, 1937 UNITED STATES PATENT OFFICE ALLOY FOR DENTAL PLATES British company No Drawing. Application January 12, 1937, Serial 7 Claims.

This invention relates to dental plates and in particular to alloys suitable for their preparation. Alloys intended for use in the preparation of dental plates must flow freely, reproduce details of the mould accurately, yield castings having a smooth surface free from blisters and have sufficient ductility to allow slight adjustments to be made to the plates after casting. The alloy should also resist the corrosive action of the usual cleaning agents and should preferably also have the property of being resistant to staining by the oral fluids, fruit juices and the like.

I have found that alloys of palladium, silver and copper containing small amounts of phosphorus fulfil the above requirements to an eminently high degree. A suitable range of alloys is that comprising from 20 to 40% of palladium, from 35 to 65% of silver, from to 30% of copper and from 0.05 to 0.25% of phosphorus.

The best results are obtained when the silver and copper are present in the eutectic ratio (approximately 2.5:1) or within 5% above or below this ratio.

25 It has been found that in order that the alloys shall have sufficient resistance to a diluted solution of the disinfectant cleaning material known under the registered trade-mark of Milton, a minimum amount of about 30% of pal- 30 ladium is necessary.

The phosphorus is preferably added as copper phosphide. It serves the purpose of improving fluidity without imparting brittleness to the castings and, by effecting more complete de- 35 oxidation, leads to cleaner castings. Furthermore the alloy can be remelted several times without becoming brittle.

The toughness of the alloys may be considerably improved by quenching them from a red 40 heat.

The following table gives a number of alloys which have proved suitable for the preparation of dental plates, but it will be understood that 45 the invention is not restricted to the particular examples given in the table. Each of the alloys has been cast into experimental dental plates by means of a Solbrig dental press. The plates have been cut into strips and tested for brit- 5 tleness by being bent through 180 (i. e. from a In Great Britain February 28,

right angle in one direction to a right angle in the other direction) with a pair of pliers. The number of bends before the strips broke are given in the table.

Number bends before break (after quench- Parts of Ag Parts of Cu Parts Parts Liquidus Solidus of Pd c. C.

9. 9. HHOOO orcnumm acumen- These alloys, especially Nos. 4 and 5, give clean, sharp castings free from brittleness, can be remelted several times without deterioration and have good resistance to the cleaning fluid known under registered trade-mark as Milton.

Experimental dental plates have been tested in the mouth and have proved extremely resistant to the oral fluids and very resistant to staining by tobacco smoke, fruit juices and the like.

What I claim is:

1. An alloy for dental plates consisting of from 20 to 40% of palladium, from 35 to 65% of silver, from 15 to of copper and from 0.05 to 0.25% of phosphorus, the amounts of silver and copper 30 being present in percentages within 5% above or below the eutectic ratio.

2. An alloy for dental plates consisting of from 25 to 33% of palladium, from 40 to 53.5% of silver, from 20 to 27% of copper and from 0.05 to 0.15% of phosphorus, the amounts of silver and copper being present in percentages within 5% above or below the eutectic ratio.

3. As a new article of manufacture, a dental plate consisting of from 20 to of palladium, 40 from 35 to 65% of silver, from 15 to 30% of copper and from 0.05 to 0.25% of phosphorus.

4. An alloy for dental plates consisting of from 25 to 33% of palladium, from 40 to 53% of silver, from .20 to 27% of copper and 0.05% of phosphorus.

5. An alloy for dental plates consisting of from 25 to 30% of palladium, from to 53.5% of silver, from 20 to 21.5% of copper and 0.15% of phosphorus. 50

6. An alloy for dental plates consisting of 30% of palladium, 50% of silver and 20% of copper which has been melted with the addition'of from 0.05 to 0.15 part of phosphorus for each 100 parts 5 of the alloy. 0 V

7. An alloy for dental plates consisting of 25% of palladium, 53.5% of silver and 21.5% of copper which hasvbeen melted with the addition of from'0.05 to 0.15 part of phosphorus for each 100 parts of the alloy.

ALAN RICHARD POWELL. 

